If you're planning an extensive multi-panel UI with dozens of options on each panel -- for example, Grid's config UI -- then I'd suggest using AceConfig or, if you're a serious masochist, AceGUI directly.

If you're planning a single panel, I'd suggest just writing it yourself using Blizzard templates (see PetBattleAutoForfeit for an example).

If you're planning a few panels with a few options each, I'd suggest either writing it yourself using Blizzard templates, or using some mini-libs to simplify generating the widgets, like tekKonfig (see StealYourCarbon or some of Tekkub's other addons) or PhanxConfig (see ShieldsUp for an example).